Refrigerator Advice

> So my conclusion after all of this is that an electric fridge will work for our uses.... EXCEPT for our 3-4 days in Yellowstone without hook ups.
> But I don't really want to invest a great deal of money to get us set up just for those few days when most of our use will be on shore power.
>
> So I'm trying to think outside of the box now for those several days. What if I bought a block of dry ice right before entering Yellowstone and
> stuck it in the fridge? Perhaps that would maintain the temp in the fridge well enough that it wouldn't have to run as much and enable us to make
> it through. Remember, I do have the genset and will be driving the GMC around the park every day as well.
>
> Thoughts? Anyone ever tried this before? (Thanks for playing along with all of my hypothetical questions!)
Driving around every day will reduce the amount of time the Onan will need to be ran. For that once a year to scrape by a day at a time for 4 days,
you could probably get by with running the generator for a few hours a day to put enough charge in the house battery to get by for mostly another 24
hours.

Jerry Work seems to have a better battery charger than the typical RV set:

http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&th=38277&start=0&rid=2083

He also recommends a good battery monitor. A good one is not cheap. Your call.

You probably won't get as good a charge in 3 hours as Jerry does, but you can run the Onan another hour or so if drivng and 3 hours of generator run
time isn't enough. You will figure out in a day or two what works for you.

If the trip home from Yellowstone is long enough, the house battery should get charged completely. Chronically undercharging will shorten the life of
a battery, but a few days of not being topped off shouldn't kill them graveyard dead. Think in terms of COMPLETE charging at least once a week, or you
could need a new house battery every camping season.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"Highest price does not guarantee highest quality."
 
> Here photo's of the installed Votronic VCC 1212-45, which does a good job in charging the batteries while driving.
> And has a Characteristic Line of Charging: IU1oU2
>
> The most easy way to understand its function, is to compare it to a state of the art 110/120v Battery charger, but now the input is not 110/120v
> but the available current from the alternator. And giving that alternator a lower chargelevel of the battery, by "fooling" it, and letting it still
> keep charging, even if the starterbattery is full (and that mostly happens very fast) Controling and transforming those current and amps to a higher
> level if necessary.
> Info at: http://www.votronic.de/index.php/en/products2/series-vcc/standard-version/vcc-1212-45
>
> [......................]
> Daniel

Here some additional info:

http://www.votronic.de/Library/Catalogue-Sites/Charging-Converter.pdf

Note: They dropped the 25 Amps and switched to a 30 Amps 1212 version.
Also more types for the LitiumIon batteries.

ICW a 12v or 120v with inverter Fridge I see very quick and strong charging during our trip.
ICE you could even let your engine running at idle, and still get maximum charging.

Daniel
--
Daniel Jacobs, No GMC, but an admirer of them .... We'll see what the future brings ....

Always remember, the world is full of nice people!
So, if you can't find one, be one!
 
> So my conclusion after all of this is that an electric fridge will work for our uses.... EXCEPT for our 3-4 days in Yellowstone without hook ups.
> But I don't really want to invest a great deal of money to get us set up just for those few days when most of our use will be on shore power.
>
> So I'm trying to think outside of the box now for those several days. What if I bought a block of dry ice right before entering Yellowstone and
> stuck it in the fridge? Perhaps that would maintain the temp in the fridge well enough that it wouldn't have to run as much and enable us to make
> it through. Remember, I do have the genset and will be driving the GMC around the park every day as well.
>
> Thoughts? Anyone ever tried this before? (Thanks for playing along with all of my hypothetical questions!)
One thing no one mentioned was using a small portable generator instead of the Onan for that trip to Yellowstone. The high-pitched whine might be more
annoying than the Onan grumble, but a 1kW set would charge your house battery bank in the same amount of time on less gas than the Onan. Or the
smaller set might seem quieter than the Onan, since you can put it as far from people as the extension cord allows.

Its all about battery physics and charger electronics. The faster you try to charge a battery, the less efficient the charging process. The faster you
pull current out of a battery, the less efficient the energy transfer. A 40A converter charger won't put more than 40A into the battery. So if it is a
100 Amp-hour battery that is "empty", and it needs 100 amp-hours, it would take that 40A converter charger 2-1/2 hours to charge it (more because of
internal battery losses). It will take 2-1/2 hours whether the converter/charger is running on Onan power or a 1kW whiner. Also remember that the 40A
from the 12V side of the converter/charger only represents a little over 4A on the 120V side. That's around 500 watts. Sort of overkill to run a 6kW
genset for .5kW of power.

OTOH, if you still have the electric water heater, you will want to run the Onan for at least 20 - 30 minutes to heat water for a shower anyway...
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"Highest price does not guarantee highest quality."
 
OK, I looked.

Norcold 653
Dometic RM3800

Both automatic three - way which work well. The Dometic is a bit more automatic, the Norcold requires you to tell it to work on 12V DC. Both favor
110 when it's available. If I read the book right, the Dometic will automatically use the 12 volts when the engine is running, propane burner when it
isn't. I'm not positive about that .. but it doesn't kill the batteries.

--johnny

--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
I wanted to give an update on this post. I went ahead and purchased the GE Model # GCE06GSHSB 5.6 sq ft compressor fridge to run off an inverter in
my GMC. I got it home and put it on a Kill-A-Watt and I am surprised that it seems to be even more energy efficient than the Energy Guide tag. I ran
it for a couple of hours to let it get cold and then started the meter. When it runs it starts with an 80 watt draw and then drops down to 60 watts.
I have been opening the door every once in awhile to try and simulate use (although I don't have any food in it which I think would help it use less
energy).

I have now been running it for 6 hours and the meter just flipped to 70 watts used! It really doesn't cycle on very often at all. The house is at 70
degrees and like I said, the fridge is empty. So with an average use of just 12 watts an hour what should I be expecting to see as an AH draw off my
batteries? I always get confused off the amp conversion calculations. Multiplying or dividing by 12 or 10 or something?

The fridge is meant to be built in under a counter so the clearance on the sides, top and back is 0. I'm thinking of putting some foam board around
it to provide even better insulation for it.

--
-James Palmer, Traverse City, MI
1976 Eleganza
 
> I wanted to give an update on this post. I went ahead and purchased the GE Model # GCE06GSHSB 5.6 sq ft compressor fridge to run off an inverter
> in my GMC. I got it home and put it on a Kill-A-Watt and I am surprised that it seems to be even more energy efficient than the Energy Guide tag.
> I ran it for a couple of hours to let it get cold and then started the meter. When it runs it starts with an 80 watt draw and then drops down to 60
> watts. I have been opening the door every once in awhile to try and simulate use (although I don't have any food in it which I think would help it
> use less energy).
>
> I have now been running it for 6 hours and the meter just flipped to 70 watts used! It really doesn't cycle on very often at all. The house is at
> 70 degrees and like I said, the fridge is empty. So with an average use of just 12 watts an hour what should I be expecting to see as an AH draw
> off my batteries? I always get confused off the amp conversion calculations. Multiplying or dividing by 12 or 10 or something?
>
>
>
>
>
> The fridge is meant to be built in under a counter so the clearance on the sides, top and back is 0. I'm thinking of putting some foam board
> around it to provide even better insulation for it.

James,

The first part is easy, 70 Watts of AC is 70 Watts of DC (except for the conversion efficiency of the inverter you buy). I am running mine with a
Hazard Fright POS rated at 750/1500 and it is about 50$ when it isn't on sale or you don't have a 20% off coupon. Because that is a modified square
wave (sine wave my ass) box, I see less efficiency on the inverter. But when I compare it to what the Nocold would do on that same house bank, it
just isn't worth any effort to improve it.

Back to the house bank load. 70 Watts is going be about 6 amps of DC and the duty cycle comes to get you when it is warm. If the house bank is not a
pair of GC2s (or better), plan on making it so. The Peukert exponent is not in your favor.

What you didn't look at was the starting inrush of the compressor. Set the Kill-A-Watt to monitor current and wait for the compressor to cycle. (If
you turn it off and on yourself, you may be too fast and that makes a bidder load.)
Believe you eyes!! If running is less than an amp, the starting load can be 10 on line power - it will be at least 5. Now though the inverter, that
gets the times 10 you have heard of. So, that starting current is suddenly 100amps. That is the 1200 Watts that is why you want the 750/1500
inverter. Oh, the inverter should be as close to that house bank as you can get it and have it in a protected space and not exposed to the batteries.
And, USE BIG wire for the feed.

If you want to know more about this foolishness, I'm here and I have had an installation I would call successful for some years now.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
That 70 watts was the total that the fridge used in 6 HOURS! That boils down to 12 watts or so an hour. I've tested the Kill-A-Watt on light bulbs
and it is functioning correctly.

As to inverters, I have a Xantrex 600 watt Pure Sine Wave Inverter that will be installed right above the battery bank in the back. I chose this
inverter as it will also be used for my wife's CPAP machine and from what I understand pure sin is better for these. I have a 12 gauge ext cord that
will run behind the seats and bathroom to where the fridge will live.

I've been trying to catch the starting amps when it cycles on but it only come on every 30 or 40 minutes so unless I want to spend my evening staring
at a Kill-A-Watt I might never catch it. I suppose I could unplug it and leave the door open for a few minutes. But by my math it's only using
around an amp an hour? Could this be correct???
--
-James Palmer, Traverse City, MI
1976 Eleganza
 
> I wanted to give an update on this post.
> I have now been running it for 6 hours and the meter just flipped to 70 watts used! It really doesn't cycle on very often at all. The house is at
> 70 degrees and like I said, the fridge is empty. So with an average use of just 12 watts an hour what should I be expecting to see as an AH draw
> off my batteries? I always get confused off the amp conversion calculations. Multiplying or dividing by 12 or 10 or something?...
I spent 40 minutes typing something to explain watts, watt-hours, amps, amp-hours, and volts.

I gave up. Your eyes would glaze over and you wouldn't absorb it. So here's what you are going to do.

"Install" it, run it and the other 12VDC loads in real use until the battery needs to be recharged, and note how long that took. Then run the Onan for
4 hours, or use whatever your backup charging system is.

Even though it seems to be as energy efficient as an RV fridge, between it and the other 12VDC loads, it won't last a full two days unless you have
two each 6V golf cart batteries in series as your battery bank. Then it might go more than two days.

Forget watts. Batteries are rated in amp-hours. Divide watt-hours by 12 to get amp-hours. I am guessing when you said "70 watts" you meant 70
watt-HOURS. That would be about 5.83 amp-hours. Divide that by 6 hours and you get about 1 amp average draw. A 100 amp-hour battery can lose 50
amp-hours before it is graveyard dead. Or 50 hours at 1 amp average draw (two days and two hours). Since other stuff will be sucking amp-hours out of
that battery, it won't as long as that math suggests.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"When I grow up I am going to be a curmudgeon."
 
Oh yeah. I forgot to mention that now that you don't have a propane fridge, you are going to want to reconfigure the fridge compartment and seal up
the side and top vents and allow for living space air to flow over the coils. In at the bottom front and out at the bottom front.

You also want to insulate that exterior wall behind the fridge better than it is insulated now.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"When I grow up I am going to be a curmudgeon."
 
This is an extremely good thread. I want to thank everyone for their thoughts and input. This is the extreme value of the forum. I have no plans along
this line, but interested in electrons.
May be late to the issue, you could install a much smaller propane tank and pick up storage room, still using a gas frig.
Or, think of the batteries that could occupy the vacated space.
Tom, MS II
--
1975 GMC Avion
KA4CSG
 
I've already removed the stove and will be using an electric induction cooktop when on Shore Power (we will be on shore power most nights when we
camp) so by using an electric compressor based fridge I eliminate the propane tank altogether (I know this is heresy to some!). So I will gain
storage space where the tank used to be as well as to seal off the openings behind and above the fridge to make the GMC better insulated.

My one worry was about the energy consumption of a compressor based fridge but this GE one seems to be using about an amp an hour so I'm really stoked
about it. Of course it's smaller than what GMC's originally had but my family has made do with a mini fridge during kitchen renovations and I believe
the 5.6 cu ft will work fine for us. (We don't drink beer or pop and that's half of most peoples fridges right there!!!) Have to have the Pure Sine
inverter for my wife's CPAP anyways, might as well put it to work. Time to build the battery bank!
--
-James Palmer, Traverse City, MI
1976 Eleganza
 
I find electric stoves anathema and electric heaters slow, so my propane tank will remain - plus the PO installed a new Suburban furnace which will
run you out in ten minutes. However, when the Dometic icebox dies, I'm going to lay in one like you have, and add a little inverter to run it. My
dry camping is up to two weekend shows a year now, and isn't likely to increase.

--johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
If what I am saying turns out to be confusing, then ignore this posting.

I keep reading things that you have posted and the terminology you are using is sometimes incorrect. It may just be a wording issue rather than a
conceptual issue.

If your refrigerator is using 70 watts when running and higher when starting, then you need to plan the sizing and length of the wiring, and
components (primarily the inverter) with that in mind.

Since a refrigerator does not run all the time we express how much energy in consumed used in "watt-hours". With that "Kilowatt meter" that you are
using you can measure current watts being used (watts) at any give time, and total "watt hours" being used over time.

So if you use 70 "watts" when running but only ran for 6 minutes per hour (1/10 of an hour), then your power consumption per hour would be 7
"watt-hours" because the refrigerator only ran 10% of the time.

The same thing goes for "amps" and "amp-hours". At 70 watts you will be using around 6 amps (at 12 volts) DC when the refrigerator is running and 0
amps when the refrigerator is not running. So if the refrigerator only runs 6 minutes in an hour (1/10 of an hour) at 6 "amps", the power consumption
would be 1 "amp-hour".

What makes it more confusing is sometimes we state capacity or consumption in "watt-hours" and sometimes we use "amp-hours". The only difference
between the two is "watt-hours" and "watts" is "amp-hours" and "amps" multiplied times the supplied voltage which in this case is 12 vdc.

I think you already have the concepts down but the terminology in the postings was confusing me. I just wanted to make sure that you had the concept
correct.

I ignored the inverter power losses in the above examples.

I hope I did not confuse you more.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Thanks Ken. Sorry for my crude terminology. I think I follow your explanation.
--
-James Palmer, Traverse City, MI
1976 Eleganza
 
> Thanks Ken. Sorry for my crude terminology. I think I follow your explanation but have one question. You said that the 70 watts running for only
> 1/10 of an hour would be 7 watt hours which I get. Then you said 6 amps at 1/10 of an hour would be 1 amp hour, but wouldn't this be 0.6 amp hour
> with those numbers? I'm not sure how long the fridge runs every hour so instead of looking at what it is using while it runs I am looking more at
> the meters record of what it has used over time.
>
> At this point the fridge has been plugged into the Kill-a-watt meter for 24 hours and it has recorded that it has used 250 watt hours. If I
> divide the 250 watt hours by 12 vdc I get nearly 21 which if I'm following correctly is the number of amp hours that would have been drawn off my
> battery in a full 24 hour day. With inverter loss call it 24 amp hours per 24 hour day.
>
> Sure it might be hotter during the day than my 70 degree house but where we camp it also tends to get pretty chilly at night. And I will have
> food packed in it and additional foam around it (as it's 0 clearance) so that should help too. Either way I'm pretty excited at how efficient this
> compressor fridge is!
Stop being confused. Ken was thinking it was sucking 70 watts when running and ran like that for six hours, and that is 5.83 amps for 6 hours, or
almost 35 amp-hours (which would drain the battery dead in about 9 hours). Watts means instantaneous energy consumption RATE. RATE is energy units
divided by time. To get energy, you need to multiply that RATE by the amount of time it ran at that RATE. To get actual energy consumed over time, you
multiply watts (RATE) times hours to get watt-hours. Divide watts by 12 to get amps. Batteries are rated in amp-hours. The AVERAGE number of amps
pulled over time, multiplied by time, gives you how many amp-hours have been sucked out of the battery (kind of a misnomer, the battery actually
pushes the electrons out, but I usually say the appliance sucks them out).

Instantaneous amperage being sucked from the battery is irrelevant at numbers less than ten. If it pulls 6 amps for 10 minutes and then stays off for
50 minutes, that's the same as 1 amp for an hour. 1 amp-hour. To figure out how long your battery will last, you need to figure AVERAGE drain for
appliances that cycle. Since a kill-a-watt can't measure current on the DC side, just divide watt-hours by 12 to get amp-hours. Oh yeah. There is some
loss in the inverter that the kill-a-watt can't measure. Maybe 15% or more, so you need to add that to your amp-hour draw numbers. And an inverter
sucks DC power even under no AC load. As you can see, the amount of time your battery will last is shorter than you think. You are going to have to
try it all out under real world conditions to get reality.

Try camping in the driveway for a weekend where you can retreat to the house if you need to abandon ship.

You really need to measure the power consumed by that CPAP machine. It could very well be more than that fridge. Between the fridge and the CPAP
machine, you might run the battery down overnight, and you don't want that CPAP machine to stop.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"When I grow up I am going to be a curmudgeon."
 
I think you are correct. I think I confused myself in trying to explain amp and amp-hours. .6 number appears to be correct in that example that we
used. I was concentrating on making the explanation as simple as possible and got lost doing the math.

The rest of your math also appears to be correct.

Since most of the refrigerator is inside the coach, outside temperatures should not have a large effect on it's operation. There is not much you can
do about that variable so I would not worry too much about it.

I cannot give you any real world experience on battery longevity. I have a propane powered refrigerator so I do not worry about running house
batteries down. I just fill up the tank every 3 years or so.

I'm sorry for the math error but it is good that you understood what I was trying to say and corrected my error.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
No worries! Your explanation was great and I thought "I'm getting it" and then I ran into that and thought, "Shoot, maybe I missed something and
don't get it after all!" Math is not my strong suit. Love how helpful everyone is on here.
--
-James Palmer, Traverse City, MI
1976 Eleganza
 
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